This invention pertains generally to guidance systems for guided missiles, and in particular to a system for testing such missiles when used against airborne targets.
At various times during the development of guided missiles (referred to hereinafter simply as missiles) to be fired at airborne targets the missiles must be tested. During a full, successful test of such a missile, the missile may be fired to intercept a drone aircraft. Because the result of an intercept usually means destruction of both a sophisticated and costly drone aircraft and missile, testing must be limited for economic reasons.
Less costly test strategies have been developed which allow testing of the sophisticated missile guidance systems without actually detonating the missile and destroying the drone aircraft. Thus, additional equipment may be added to the drone aircraft and the missile under test to measure the point of closest approach between the missile and the drone aircraft. The resulting test data may be used to verify that the guidance system brought the missile close enough to a drone aircraft. The resulting test data may also be used to determine the effectiveness of electronic jammers or other countermeasures used to intentionally make the missile miss the drone aircraft.
In one test configuration, radar on the drone aircraft may be used to track the the approach of the missile. That configuration, however, performs poorly when the target is at a low altitude because of radar reflections from the ground. In a second test configuration, a mono-frequency transmitter may be mounted on the missile under test with receivers mounted on the drone aircraft. Four non-coplanar receivers measuring the signal from the missile as the missile approaches the drone aircraft may gather enough data to allow calculation of the position of the missile relative to the drone aircraft. The miss-distance may then be determined by finding the trajectory of the missile that produces a history of signals matching the history of the signals actually at all four receivers. The second test configuration suffers from the effects of high noise signals induced in the received signals as the drone aircraft maneuvers while attempting to evade the missile. Thus, as the aspect angle of the drone aircraft changes, some receivers may be momentarily shielded from the transmitter so that the signal then measured by the shielded receiver is essentially noise. Noise may also be introduced when multi-path effects are present.